The present invention relates to a film processing apparatus, which may be utilized with a telecine apparatus for generating television signals from a movie film, a movie projector, and so forth, and, more particularly, to such apparatus which detects positioning errors of a running movie film and corrects the position of the film in accordance therewith, and provides a film path such that the film is protected from damage and enables high quality film processing.
Film processing apparatus may utilize a film feeding system (such as a continuous film feeding system and an intermittent film feeding system) depending on the type of apparatus. For example, a telecine apparatus generally uses a continuous film feeding system, and movie projectors which project pictures of a lighted movie film directly on a screen frame by frame use an intermittent film feeding system.
The continuous film feeding system uses a capstan for feeding a movie film at a constant rate. A telecine apparatus using such system lights the movie film with a light in a repeating one-dimensional vertical scanning arrangement in the film feeding direction. Consequently, the movie film is picked up frame by frame in such cluster scanning order and supplied to light receiving elements so as to generate television signals from the movie film.
On the other hand, the intermittent film feeding system uses rectangular openings called perforations formed on both sides of the film for feeding the movie film frame by frame intermittently. For movie projectors using this system, a cam mechanism may be used to insert pins called registration pins into the perforations of the film and to drive the same so as to feed the film intermittently. Furthermore, synchronized with this intermittent feeding of the film, a light is projected intermittently on the film from a light source and the transmitted light from the film is projected on a screen.
The continuous film feeding system has an advantage in that a relatively small load is applied to the film because there is no repetition of feeding and stopping the film. However, it has a disadvantage in that the lighting may not be properly synchronized with the feeding of the film. Thus, the continuous film feeding system may cause jitters in the longitudinal direction of the film and flickering which may result in shifting or distortion of pictures. Furthermore, for a telecine apparatus using a so-called flying spot scanner for scanning pictures by projecting a spot-like light on the film, the accuracy may vary and the life may be shortened depending on the operation hours, temperatures, and other conditions of the apparatus. As a result, troublesome and costly periodical maintenance and inspection are needed for such apparatus.
An intermittent film feeding system may simplify the configuration of the optical system and the film feeding system, but may require laborious adjustment to correct the positioning of the registration pins so as to engage the perforations of the film. Unless registration pins are positioned correctly, the film may be damaged by the registration pins. Further, such apparatus may produce large and bothersome mechanical sounds.
The above intermittent film feeding system also has a problem in that pictures projected on a screen may vibrate and shift each time a frame is fed, or may gradually go up/down from an initial position (hereafter, displacement of a picture caused as a result of processing in the apparatus is referred to as picture shift). Such problem may not be prevented completely. As is to be appreciated, picture shift deteriorates the quality of pictures projected on a screen by a movie projector, which is typically unacceptable to an audience.
In a telecine apparatus, this picture shift is converted to video signals which cause still pictures to seem as if they are vibrating which, in turn, may causing the frequency to become high when such video signals are compressed and causing an unnecessary increase in the amount of data. Furthermore, when digitizing pictures, the desired effect cannot be obtained if the object to be edited, which is expected to be at a certain same position, vibrates.
Therefore, in a film processing apparatus, it is desirable that the film guided by a guiding unit is positioned correctly. A position detector has been proposed for detecting whether or not the object film is positioned correctly. In the position detector, a plurality of electrodes are provided at the edge of the film and a conductor facing these electrodes is provided across the film. A condenser is formed with these electrodes and the conductor may be used as polar plates spaced with the film thickness. The capacitance of the condenser, which varies according to change in the film position, is used for detecting the film position on the basis of the amount of the capacitance variation.
However, a movie film often expands and contracts depending on environmental conditions like temperature, humidity, and so forth. These conditions may cause the positioning accuracy to be lowered.
Furthermore, perforations are apt to deform as the film is used for a long time. Additionally, foreign objects may also stick on the film surface. Even if a plurality of electrodes are arranged so that perforations cross between these electrodes to detect film positioning errors according to the capacitance formed between these electrodes, the above deformation and stuck foreign objects of the film may locally change the thickness of the film which may cause the film positioning accuracy to be significantly lowered.
A movie film has a dielectric constant and a thickness which may be dependent upon the film material and, as such, may be different from that of other films. Since the relation between film positioning error and capacitance changes due to such film characteristics, correct positioning error detection may not be obtained.